Methods for separating material from a mold surface

ABSTRACT

Apparatus and method for removing unwanted excess material from a mold section is particularly adapted for removing a monomer ring adhered within a reservoir of a female mold section used to mold a contact lens. The invention involves piercing the monomer ring and rotating the piercing members (e.g., annularly spaced pins) relative to the mold section whereby the monomer ring is sheared from the mold section to which it was adhered while the molded lens is left intact in the mold section.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to molding of articles ofmanufacture, and more particularly relates to methods and apparatus forseparating excess, unwanted lens material from a mold surface. Thepresent invention has particular application to the production of moldedophthalmic lenses such as contact lenses and intraocular lenses.

[0002] Static cast molding of contact lenses is known. See, for example,U.S. Pat. No. 5,466,147 issued to Bausch & Lomb Incorporated, the entirereference of which is incorporated herein by reference. A single moldunit for making a single lens comprises a female mold section having aconcave optical surface and a male mold section having a convex opticalsurface. The female and male mold sections are complimentary shaped andare brought together to form a lens-molding cavity between the facingconcave and convex optical surfaces of the female and male moldsections, respectively.

[0003] Although less popular than full cast molding, forming lenses byspin-casting is also known where lens material is deposited into afemale mold section and spun to form the anterior surface of the lens.The posterior surface is then formed by a lathe cutting operation. Inthis method of lens manufacture, excess material may also form on thefemale mold section with may require removal prior to lens release fromthe mold.

[0004] The basic process for cast molding a lens is as follows. Aquantity of liquid lens material is dispensed into the concave opticalsurface of the female mold section and the male mold section is seatedupon the female mold section with the concave and convex surfacesthereof facing one another to form a lens-shaped mold cavity. The joinedfemale and male mold sections form a single mold unit which is subjectto a curing cycle (e.g., by thermal or UV radiation) thereby causingpolymerization of the lens material in the mold cavity. Once the lensmaterial has cured, the male and female mold sections must be separatedto retrieve the cured lens.

[0005] The opening or release of the mold sections must be carried outin a manner which will not harm the delicate lens. Once the lens haspolymerized in the mold cavity, the lens and any excess lens materialwill have an adhesive bond to the opposite concave and convex moldsurfaces. Thus, the release of the male mold section from the femalemold section must be of a force strong enough to break the adhesive bondof the lens and excess lens material to the opposing mold surfaces, yetnot so forceful or haphazard that the optical surfaces of the lens areharmed by the release process. Should the lens crack or be otherwisedamaged during the mold release process, the lens must be scrapped,thereby lowering the output yield and increasing manufacturing costs.

[0006] Once the mold sections have been separated, the lens will adhereto one of the mold surfaces and must therefore be released from the moldsection on which it is retained. Both wet and dry release methods oflens release have been proposed in the prior art. In wet lens releasemethods, an aqueous solution is used to wet the hydrophilic lens whichabsorbs water and swells, causing the lens to separate from the moldsurface. In dry release methods, the lens is removed from the associatedmold surface while still in the dry state. The adhesive bond between thelens and mold surface is broken, usually by application of a force tothe mold body, for example by squeezing or pressing against thenon-optical surface of the mold to move the mold surface relative to therigid lens. Once the adhesive bond has been broken, the lens isretrieved, for example by a vacuum picking tool.

[0007] To ensure that the mold cavity is completely filled with theliquid lens material during the molding process described above, thequantity of liquid lens material dispensed in the female mold section ispurposely greater than that needed to form the lens. When the male moldsection is seated upon the female mold section, the excess liquid lensmaterial is expelled from the mold cavity. This excess liquid istypically held in a reservoir, groove or flange surrounding the moldcavity and is cured along with the lens. The cured excess material istypically referred to as a “monomer ring” or “hema ring” in the contactlens art depending on the specific lens material used. The term “monomerring” will be used herein for convenience, although it is understoodthis term is used broadly herein to cover any type mold materialemployed.

[0008] During mold separation, the monomer ring will usually adhere toone of the mold sections with the monomer ring usually retained in thefemale mold section along with the lens. Should the lens be released andremoved from the female mold surface without prior removal of themonomer ring from the reservoir, the lens edge will likely be damageddue to interference with the monomer ring. This problem is illustratedin prior art FIG. 5C herein. It is thus desirable to release and removethe monomer ring from the female mold section prior to release andremoval of the lens therefrom.

[0009] Various monomer ring removal processes have been employed in theprior art, none of which has proven very satisfactory.

SUMMARY OF THE INVENTION

[0010] The present invention is directed toward a method and apparatusfor removing a monomer ring from the mold section to which it is adheredfollowing mold separation. The monomer ring may be located on a flange,groove, or reservoir surrounding the molding surface.

[0011] The present invention is particularly useful for removing curedexcess material formed in contact lens or intraocular lens molds,although it is equally applicable to other molds requiring removal ofexcess material. Excess material in an ophthalmic mold, also known as amonomer ring, can cause damage to the molded lens if the monomer ring isnot released and removed from the mold section prior to release andremoval of the lens from the mold section.

[0012] In the preferred embodiment, following the curing stage, the moldis opened and the mold section to which the monomer ring and lens areadhered is presented for removal of the monomer ring while leaving thelens unharmed and intact. The monomer ring is removed by a plurality ofsharp members (e.g., pins or blades) which descend from a locationdirectly above the mold section to pierce the monomer ring but not sodeep as to penetrate the mold section. The pins then rotate which shearsthe monomer ring free of the mold section. The pins are then raised,carrying the monomer ring along with it for disposal. Thereafter, thenow monomer ring-free mold section having the lens adhered thereto istransferred to a lens release station and further downline processing asdesired.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a perspective view of a prior art contact lens moldcomprising a male mold section spaced above a lens and a female moldsection;

[0014]FIG. 2 is an enlarged, cross-sectional view of the female moldsection of FIG. 1;

[0015]FIG. 3 is an enlarged, fragmented, cross-sectional view of a priorart contact lens mold in the process of molding a contact lens therein;

[0016]FIG. 4 is the view of FIG. 3 showing the mold in the fully closedposition;

[0017]FIGS. 5a-c are enlarged, detail views of the reservoir area of themold of FIGS. 1-4 in sequential process steps of lens cure, moldseparation and lens and monomer ring release, respectively;

[0018]FIG. 6 is a perspective view of an apparatus for carrying out themethod of the present invention;

[0019]FIG. 7 is a top plan view of FIG. 6 with certain parts not shownfor clarity;

[0020]FIG. 8 is a cross-sectional view of the apparatus as taken alongthe line 8-8 in FIG. 6; and

[0021]FIG. 9 is an enlarged, detail view of the part of the apparatus ofthe present invention which engages the female mold section in theintended manner.

DETAILED DESCRIPTION

[0022] Referring to FIGS. 1-5, a prior art mold 10 for cast molding anophthalmic lens 12 is seen to comprise a female mold section 14 having aconcave optical surface 14 a and a male mold section 16 having acomplimentary shaped convex mold surface 16 a. In cast molding of anophthalmic lens 12, a liquid lens material 18 is dispensed into theconcave surface 14 a of the female mold section 14. The male moldsection 16 is seated upon the female mold section 14 until the moldsurfaces 14 a, 16 a thereof are closely adjacent as seen in FIG. 4. Asthe mold surfaces move toward each other, excess liquid lens material isexpelled into a reservoir 20 located peripherally of the mold surfaces14 a, 16 a (FIG. 4). U.S. Pat. No. 5,466,147 discloses such a mold formolding lenses, especially contact lenses. Upon polymerization, the lensmaterial between the mold surfaces 14 a, 16 a is cured to form a lens 12(FIG. 1), together with the excess lens material 18′ located inreservoir 20 which, in the cured state, is referred to as a monomer ringdenoted by reference numeral 18″ seen in FIGS. 5a-c.

[0023] The '147 patent recognized the problems associated with theattempted removal of the lens prior to removal of the monomer ring froma mold section which is illustrated herein in FIGS. 5a-c. FIG. 5aillustrates opening of the mold once the lens material has been curedwhere the male mold section 16 is lifted from the female mold section14. As is typically the case in this type of mold design, the lens 12and monomer ring 18″ remain adhered to the female mold section 14. Inthe mold design of the '147 patent, the female mold section includes aknife edge 14 b which interacts with an annulus 16 b formed on the malemold section 16 to form the lens edge 12 a. As seen in FIG. 5c, removalof lens 12 from the female mold section 14 without having first removedthe monomer ring 18″ may result in accidental engagement between thelens edge 12 a and the monomer ring 18″ which could irreversibly damagethe lens edge 12 a. This problem is exacerbated when a wet lens releasemethod is employed which involves hydrating the lens which swells andreleases from the female mold surface. Due to the swelling of the lens,the lens edge may push against the monomer ring and be damaged thereby.Although the problem is pronounced in the wet lens release method, thereremains the chance of lens damage in a dry lens release method as well.

[0024] The '147 patent describes a method of releasing the monomer ringwith removal of the male mold section by incorporating a feature intothe male mold section to which the monomer ring will attach upon cure(see feature 79 in FIGS. 18 and 19 therein). In the '147 method, themonomer ring detaches from the female mold section upon lifting the malemold section therefrom. Since it is not always possible to incorporatethis type of monomer ring removal mechanism in a particular mold design,the present invention offers a method of monomer ring removal from thefemale mold section which may be employed on molds having a variety ofdifferent mold designs.

[0025]FIG. 5b illustrates an enlarged cross-sectional area of the femalemold section 14 where the lens edge 12 a and monomer ring 18″ lie withinthe female mold section following removal of the male mold section 16therefrom. The female mold section 14, lens 12 and monomer ring 18″ isin this condition upon presentation to the apparatus and method of thepresent invention for removing the monomer ring 18″ therefrom, thepreferred embodiment of which is illustrated in FIGS. 6-9.

[0026] A monomer ring removal mechanism is indicated generally by thereference numeral 30 which may be mounted upon a table 32 which is partof a contact lens production line. Upstream and downstream processingmay vary according to need and is not critical to the operation of theinvention described herein. Typical upstream processing would includemold production, monomer fill of the mold, mold clamping and curing, andopening of the mold. Once the mold has been opened, the male moldsection 16 is set aside and the female mold section 14 is presented tothe monomer ring removal mechanism 30. Once the monomer ring has beenremoved by mechanism 30 in the manner to be described, the female moldsection 14, now having only a lens 12 adhered thereto, is transferred tosubsequent processing stations such as lens release, with the lensfurther undergoing lens hydration and extraction, lens packaging andinspection as required for the particular production process employed.

[0027] As seen in FIGS. 6 and 7, the monomer ring removal mechanism 30may be mounted upon a table 32 having a rotating carousel 34 forhandling of the female mold sections 14 through this station, althoughother mold handling means may be employed as desired. In the embodimentof FIGS. 6 and 7, the female mold sections 14, with respective lens 12and monomer ring 18″ intact, are delivered onto table 32 at location 36(e.g., by a conveyor 46). As a female mold section 14 is delivered ontotable 32, carousel 34 is indexed in the direction of arrow 35 whereuponfemale mold section 14 is captured by one of a plurality of peripheralrecesses 34 a in carousel 34 and move together with the next indexingmovement of the carousel 34. This is continued with each successiverecess 34 a engaging a respective female mold section 14 at input 36. Toensure limited radial movement of the female mold section 14 within arespective recess 34 a, a spool 38 may be fixed to carousel 34 adjacenteach recess 34 a which restrains the respective female mold section 14as the carousel is indexed about table 32.

[0028] Mechanism 30 is shown mounted to table 32 at a locationapproximately 180° from the mold section input 36, although this spacingmay vary as desired. The positioning of the mechanism 30 is such thateach sequential recess 34 a will come to rest directly beneath mechanism30 upon each indexed movement of carousel 34. As seen in FIG. 7, thelocation of mechanism 30 includes a second spool element in the form ofa biasing pawl mechanism 40, 42 which act to bear against the femalemold section to restrict substantially all radial movement thereofwithin recess 34 a during engagement of the female mold section 14 withmechanism 30. Once mechanism 30 has removed the monomer ring 18″ from arespective female mold section 14 in the manner to be described, thecarousel 34 is again indexed about arrow 35 whereupon the female moldsection 14 is eventually output from table 32 at location 44 by aconveyor 46, for example, which transports the female mold section 14and adhered lens 12 to a lens release and removal station (not shown).It will be appreciated that once a female mold section 14 has beentransported off table 32, the recess 34 a in which it was housed is nowempty as it travels again toward input 36 to capture a new female moldsection for processing by mechanism 30.

[0029] Attention is now turned to the monomer ring removal apparatus andmethod of the invention and a preferred mechanism 30 by which thismethod may be carried out. As seen in FIGS. 8 and 9, a female moldsection 14 having a lens 12 and monomer ring 18″ adhered thereto ispresented beneath mechanism 30 by action of carousel 34 as discussedabove. Mechanism 30 is mounted upon a linear slide 48 (FIG. 6) forreciprocating vertical movement of mechanism 30 with respect to table32. Once a female mold section 14 is in position beneath mechanism 30 asseen in FIG. 8, the linear slide 48 is activated which lowers mechanism30 to remove monomer ring 18″ therefrom without harming the associatedlens 12.

[0030] More particularly, mechanism 30 includes a rotary actuator 49coupled to a shaft 50 which carries a pin disk 51 having a plurality ofannularly spaced pins 52 fixed thereto and extending downwardlytherefrom. Pins 52 operate with mechanism 30 to pierce monomer ring 18″,loosen it from female mold section 14 upon rotation of shaft 50, andthen lift the ring 18″ free of the female mold section upon raisingmechanism 30 and pins 52. Any number of pins 52 may be used, however,three to four equally, annularly spaced pins 52 is most preferred. It isalso envisioned that blades or other piercing shapes may be used inplace of or in combination with pins 52.

[0031] To ensure that pins 52 pierce only the monomer ring 18″ and notthe female mold section 14 itself, a stop is incorporated in mechanism30 in the form of a guide plate 54 which is fixed relative to pins 52.As mechanism 30 is lowered, the lower surface 54′ of guide plate 54engages mold shoulder 21 located outwardly adjacent the periphery ofreservoir 20 (see also FIG. 2). Upon contact of guide plate 54 withfemale mold section 14, slider 48 stops its downward travel. By fixingthe position of guide plate 54 relative to the tips of pins 52, andknowing the distance between the surfaces of shoulder 21 and reservoir20, mechanism 30 may be calibrated to ensure the tips of pins 52penetrate only the monomer ring 18″ and do not penetrate the female moldsection 14.

[0032] A second shaft 56 telescopes within a longitudinal opening 50 ain shaft 50 and is axially movable therein. A stripper plate 57 isprovided at the lower end of shaft 56 and includes a plurality ofannularly spaced openings 57 a wherethrough pins 52 freely extend,respectively. A helical spring 58 is provided about shaft 56 betweeninternal shoulder 50 b of shaft 50 and stripper plate 57 whereby shaft56 is biased by spring 58 in a downwardly extended position relative toshaft 50. The downward travel of shaft 56 is limited by dowel 60 and inthe full downward extension thereof, the free ends of pins 52 areconcealed within the respective openings 57 a of stripper plate 57.

[0033] As slide 48 lowers mechanism 30 over a respective female moldsection 14, the lower surface 57 b of stripper plate 57 engages thereservoir surface of mold section 14 which pushes shaft 56 in upwardlywithin shaft 50. Shaft 50, together with pins 52, continues its downwardtravel until guide plate 54 engages mold surface 21 and stops furtherdownward travel of slide 48 as explained above. It will be appreciatedthat due to the upward travel of shaft 56 within shaft 50 which carriespins 52, the free ends of pins 52 extend and project through theirrespective openings 57 a in stripper plate 57 and pierce the monomerring 18″ located in mold reservoir 20. Once this has happened, rotaryactuator 49 is activated which rotates shaft 50 together with pins 52which shears the monomer ring 18″ from its associated mold reservoir 20.In a preferred embodiment, shaft 50 rotates about 180° with the monomerring 18″ shearing from reservoir surface 20 at about 10° of rotation.Slide 48 then raises with shaft 50 together with pins 52 and monomerring 18″.

[0034] Once the lower surface 57 b of stripper plate 57 has lifted freeof the reservoir surface 20, spring 58 biases shaft 56 in a downwarddirection relative to shaft 50, thereby retracting pins 52 withinrespective openings 57 a which strips the monomer ring 18″ from the pins52. If desired, a source of compressed air (not shown) may also bedelivered between shafts 50 and 56 to assist the biasing force of spring58. In order to prevent the monomer ring 18″ from free falling onto thesurface of the female mold section 14 and lens 12, one or more blowersare provided (not shown) which direct a stream of air between thestripper plate 57 and female mold section 14 which blows and directs thereleased monomer ring 18″ to a disposal chute (also not shown).

[0035] Once the monomer ring 18″ has been removed from the female moldsection 14 as described above, carousel 34 is indexed to move the nowmonomer ring-free mold section 14 toward the exit location 44 where themold section is now ready for lens release. At the same time, the nextfemale mold section needing monomer ring removal is positioned beneathmechanism 30 for removal of its monomer ring 18″ in the manner describedherein.

[0036] It will thus be appreciated that the present invention provides anovel method and apparatus for removing a monomer ring from a moldsection which may be applied in an automated production line and whichsafely and quickly removes the undesired cured material from the moldreservoir without harming the delicate lens contained therein. Althoughthe invention has been shown and described herein relative to preferredembodiments thereof, it will be appreciated to those skilled in the artthat various modifications may be made to suit a particular productionenvironment. The invention is thus not to be limited by the specificembodiments or molding applications shown and described herein, butrather should be interpreted in accordance with the spirit and scope ofthe claims which follow.

We claim:
 1. A method for removing excess material from a moldcomprising the steps of piercing the excess material with one or morepiercing members and moving the piercing member relative to the mold toshear the excess material from the mold.
 2. The method of claim 1wherein said piercing member is a pin.
 3. The method of claim 2 whereinsaid mold is configured for molding an ophthalmic lens.
 4. The method ofclaim 3 wherein said excess material is a monomer ring and said piercingmember is a plurality of annularly spaced pins which pierce the monomerring and rotate relative to the mold to remove the monomer ring from themold.
 5. The method of claim 4 wherein said mold is a female moldsection having a concave molding surface and the monomer ring is locatedin a reservoir formed peripherally of said concave molding surface. 6.The method of claim 5 wherein said mold is configured to mold a contactlens.
 7. Apparatus for removing excess mold material from an open moldhaving at least two mold sections forming a molding cavity therebetweenwhen said mold is closed for forming a molded article of manufacturetherein, said excess mold material being adhered to a surface of one ofsaid mold sections in a location adjacent said molded article ofmanufacture upon opening of said mold, said apparatus comprising: a) oneor more piercing members for piercing said excess mold material; and b)means for rotating said piercing members with respect to said one moldsection while said piercing members are piercing said excess moldmaterial and thereby shearing said excess mold material from said onemold section.
 8. The apparatus of claim 7, and further comprising alinear slide to which said piercing members are mounted, said linearslide operable to alternately lower said piercing members to pierce saidexcess mold material in said one mold section, and raise said piercingmembers to lift said pierced excess mold material from said one moldsection.
 9. The apparatus of claim 8, and further comprising means forremoving said excess mold material from said piercing members once saidlinear slide has raised said piercing members from said one moldsection.
 10. The apparatus of claim 9 wherein said removing meanscomprises one or more blowers operable to direct a stream of air in adirection across said piercing members thereby blowing said excess moldmaterial off of said piercing members.
 11. The apparatus of claim 7 andfurther comprising a first shaft to which said piercing members aremounted, and wherein said rotating means comprises a rotary actuatorcoupled to said shaft and operable to rotate said first shaft togetherwith said piercing members.
 12. The apparatus of claim 11 wherein saidpiercing members are a plurality of annularly spaced pins.
 13. Theapparatus of claim 12 wherein said pins are fixed to a pin disk mountedto said first shaft.
 14. The apparatus of claim 13 and furthercomprising a stripper plate having a plurality of openings wherethroughsaid pins freely extend, respectively, said stripper plate being fixedrelative to said pins.
 15. The apparatus of claim 14 and furthercomprising a second shaft telescoped within a longitudinal openingformed in said first shaft and axially movable therein, said secondshaft being biased in an extended position relative to said first shaft.16. The apparatus of claim 14 wherein said second shaft has a lowersurface which engages said one mold section upon lowering of said linearslide whereupon said second shaft is pushed against said bias andthereby extending said pins through said openings in said pin disk andthereby exposing said pins for piercing said excess mold material. 17.The apparatus of claim 16 and further comprising a guide plate forming astop with a surface of said one mold section to limit the lowering ofsaid linear slide at a point where said pins have pierced said excessmold material but have not extended into said one mold section.
 18. Theapparatus of claim 17 wherein said one mold section is a female moldsection for molding a contact lens and said molded article ofmanufacture is a contact lens.
 19. The apparatus of claim 8 and furthercomprising a table having mold section handling means operable tosequentially position a plurality of said one mold sections adjacentsaid piercing members such that said excess mold material is aligned tobe pierced with said piercing members upon lowering of said linearslide.
 20. The apparatus of claim 19 wherein said mold section handlingmeans comprises a rotating carousel having a plurality of annularlyspaced recesses therein configured for releasably capturing a respectivesaid one mold section therein.
 21. The apparatus of claim 20 whereinsaid carousel is indexed to sequentially position said one mold sectionsadjacent said piercing members.
 22. The apparatus of claim 21 andfurther comprising a first shaft to which said piercing members aremounted, and wherein said rotating means comprises a rotary actuatorcoupled to said shaft and operable to rotate said first shaft togetherwith said piercing members.
 23. The apparatus of claim 22 wherein saidpiercing members are a plurality of annularly spaced pins.
 24. Theapparatus of claim 23 wherein said pins are fixed to a pin disk mountedto said first shaft.
 25. The apparatus of claim 24 and furthercomprising a stripper plate having a plurality of openings wherethroughsaid pins freely extend, respectively, said stripper plate being fixedrelative to said pins.
 26. The apparatus of claim 25 and furthercomprising a second shaft telescoped within a longitudinal openingformed in said first shaft and axially movable therein, said secondshaft being biased in an extended position relative to said first shaft.27. The apparatus of claim 26 wherein said second shaft has a lowersurface which engages said one mold section upon lowering of said linearslide whereupon said second shaft is pushed against said bias andthereby extending said pins through said openings in said pin disk andthereby exposing said pins for piercing said excess mold material. 28.The apparatus of claim 27 and further comprising a guide plate forming astop with a surface of said one mold section to limit the lowering ofsaid linear slide at a point where said pins have pierced said excessmold material but have not extended into said one mold section.
 29. Theapparatus of claim 28 wherein said one mold section is a female moldsection having a concave molding surface and said molded article ofmanufacture is an ophthalmic lens.
 30. The apparatus of claim 29 whereinsaid ophthalmic lens is a contact lens.
 31. The apparatus of claim 29wherein said ophthalmic lens is an intraocular lens.